A typical gas turbine that is used to generate electrical power includes an axial compressor, one or more combustors downstream from the compressor, and a turbine that is downstream from the combustors. Ambient air is supplied to the compressor, and rotating blades and stationary vanes in the compressor progressively impart kinetic energy to the working fluid (air) to produce a compressed working fluid at a highly energized state. The compressed working fluid exits the compressor and flows towards a head end of combustor where it reverses direction at an end cover and flows through the one or more fuel nozzles into a primary combustion zone that is defined within a combustion chamber in each combustor. The compressed working fluid mixes with fuel in the one or more fuel nozzles and/or within the combustion chamber and ignites to generate combustion gases having a high temperature and pressure. The combustion gases expand in the turbine to produce work. For example, expansion of the combustion gases in the turbine may rotate a shaft connected to a generator to produce electricity.
A typical combustor includes an end cover coupled to a compressor discharge casing, an annular cap assembly that extends radially and axially within the compressor discharge casing, an annular combustion liner that extends downstream from the cap assembly, an annular flow sleeve that circumferentially surrounds the combustion liner, and a transition piece that extends downstream from the combustion liner. The transition piece generally includes an annular transition duct that extends between the combustion liner and a first stage of stationary nozzles, and an impingement sleeve that circumferentially surrounds the transition duct. An aft end of the transition piece is typically connected to an outer casing such as a turbine or compressor discharge casing. A forward end of the flow sleeve circumferentially surrounds an outer portion of the cap assembly. The forward end is rigidly fixed in position to the outer portion of the cap assembly using one or more fasteners. The aft end of the transition piece at least partially supports the liner, the flow sleeve and the cap assembly.
Although the rigid connection between the flow sleeve and the cap assembly described above is generally effective for many existing combustors, it is generally ineffective for a combustor having a combustion module which includes a fuel distribution manifold at a forward end and a fuel injection assembly that extends downstream from the fuel distribution manifold. The fuel distribution manifold partially surrounds a cap assembly within the combustor. The fuel injection assembly generally includes a flow sleeve and/or an impingement sleeve that circumferentially surrounds at least a portion of a combustion liner. A forward end of the combustion liner surrounds a downstream end of the cap assembly. The fuel distribution manifold may be connected to a first outer casing such as a compressor discharge casing and the aft end of the fuel injection assembly is connected to a second outer casing such as an outer turbine casing. The fuel distribution manifold provides structural support to the forward end of the fuel injection assembly. In particular, the fuel distribution manifold provides structural support to a forward end of flow sleeve.
As the gas turbine transitions through various operating conditions such as during start-up, turn-down and/or shut-down, the combustion module, the first outer casing and the second outer casing transition through various thermal transients which results in varying rates of thermal growth between the first and second outer casings and the combustion module. Accordingly, the combustion module must accommodate for relative motion between the fuel distribution manifold and the fuel injector assembly. As a result, a rigid connection between the flow sleeve and the cap assembly of a combustor having a combustion module is not a viable option. Therefore, an improved flow sleeve assembly would be useful.